In recent years, a mobile terminal which continues data communications (communications) while switching between a narrow area communication system (small cell) such as LTE (Long Term Evolution) and a wide area communication system such as WCDMA (Wideband Code Division Multiplexing Access) (large cell) has been put in practical use.
Such narrow area communication system which has narrow service area is not limited to LTE, and includes various communication systems, such as WiMAX (Worldwide Interoperability for Microwave Access), for example.
Moreover, such wide area communication system which has wide service area is not limited to WCDMA, and includes various communication systems, such as CDMA 2000, GPRS (General Packet Radio Service) or GSM (registered trademark) (Global System for Mobile Communications).
On the other hand, regarding a mobile terminal (portable mobile terminal) including a smartphone, a terminal communicating by, for example, switching the usable wireless communication systems in a service area in which the mobile terminal is located have become mainstream.
In the present specification, a mobile terminal includes various devices which may perform wireless communications, such as not only a smartphone and a mobile phone but also PDA (Personal Digital Assistants), a game machine, a notebook computer, a tablet and so on.
In the present specification, the wide area communication system and the narrow area communication system only present relative largeness of service areas (cells), and LTE and WiMAX are also regarded as a wide area communication system against a communication system based on femtocells which have smaller service areas, for example.
As mentioned above, communication of a mobile terminal is performed by, for example, switching the usable wireless communication systems in a service area in which the mobile terminal is located. For example, the communication is performed by switching to the cheapest and high-speed wireless communication system in the service area in which the mobile terminal is located.
A mobile terminal connects and disconnects wireless communication systems when the mobile terminal switches between wireless communication systems. Wireless (Radio) resource used by such switching may be very large, and this has a large influence on the number of accommodation user and a throughput. Further, using a plurality of wireless communication systems causes an increase of power consumption of a mobile terminal.
In other words, switching between the wireless communication systems to be used for communication by a mobile terminal causes an increase of network load for such switching process, and causes a drop of a connection rate and a throughput capable of being provided to a user. Further, for example a mobile terminal searches periphery cells outside service area, and this causes an increase of the power consumption.
In this regard, in the past, for example, a wireless communication terminal which shortens the period for a returning process into a service area, and may contribute to power-saving is proposed.                Patent Document 1: Japanese Laid-open Patent Publication No. 2008-278050        